Additive manufacturing, also known as 3D printing allows to create three-dimensional objects by depositing desired material or materials in successive layers. Prior to printing, the materials are stored in one or more reservoirs of a 3D printer and are extruded through one or more heads of the printer that move to extrude the desired materials at different points in the layer while moving in predefined paths. While the extrusion is relatively straightforward when the materials stored the reservoirs are extruded from one of the heads in isolation, the extrusion becomes more complicated when a functionally graded material (“FGM”) has to be created using 3D printing. An FGM is composite of two or more input materials whose concentrations vary in different portions of the FGM, with the portions possessing properties that are hybrids of the properties of the input materials, with the properties depending on the relative amounts of the input materials within the respective portions. Examples of functionally graded materials in nature include organic structures, such as muscle tissue smoothly transitioning into tendon to allow for a strong bond with strain-relief when connecting to a rigid bone. Similarly, in 3D printing, the ability to manufacture an FGM allows to create highly optimized part designs meant to meet bulk performance requirements, such as weight, elasticity in particular directions, and rigidity in other directions.
Creation of an FGM requires mixing two or more of the input materials in desired proportions within a 3D printer and then extruding the mix in points of the FGM where the proportions are necessary. Such mixing is performed in a chamber within the printer into which the input materials are supplied from the storage reservoirs and from which the mix is extruded through the printing head. The composition in the mix within the mixing chamber can change only at a certain rate, which is governed by the both characteristics of the printer and an initial composition of the mix, and the printer head is limited by this rate of change in being able to extrude the mix of a certain composition. Thus, if a predefined path of the extruding head requires the head to extrude the mix of compositions not compatible with the rate of change, the printer head would not be able to comply with the extrusion command and an FGM could not be printed properly without purging the contents of the mixing chamber. Such a purging would not only significantly slow down the printing process, but would also waste materials that is already loaded into the mixing chamber.
Existing techniques for planning the path of a printing head during a 3D printing do not adequately account for the ability of the printer head to extrude a required material mix at a particular point in the path. Such techniques assume that material or materials having desired properties have already been loaded into the printer's storage reservoirs. Furthermore, such techniques generally assume that that only one, or at most two, materials need to be extruded and do not consider the possibility of mixes with different compositions being extruded during printing.
Accordingly, there is a need for a way to plan a path for a 3D printer's extruding head during 3D printing that accounts for the rate at which compositions of a mix extruded from the printing head can change and is suitable for printing functionally graded materials.